The present invention relates to a printer, and particularly, but not exclusively to a portable printer which can print on a variety of surfaces.
In the state of the art, a number of printers capable of xe2x80x9cdirectxe2x80x9d printing is known. Direct printing in the context of the present invention means that the printer is placed on the image receiving medium, usually manually, and the printing means of the printer or the entire printer then scans over the image receiving medium in the printing operation. Thus, the medium is not fed through the printerxe2x80x94as in most office printersxe2x80x94but the printer moves over the medium.
Such a printer is known from EP 564297-A. The printer has an ink jet print head which scans in two orthogonal directions over the image receiving medium, onto which the printer is placed manually. The printer is connected to a computer and capable, e.g of printing addresses onto envelopes, but can also be used separately from the computer for printing data downloaded from the computer to the printer.
Another ink jet printer to be placed on a printing medium is disclosed in U.S. Pat. No. 5,634,730. This printer is provided with a keyboard for data inputting, but can also print images downloaded from a computer. The print head scans over the image receiving medium along a special path, e.g. helically or like a pendulum. DE 3142937-A refers to a so-called hand stamp which is placed manually on the image receiving medium. It can print data downloaded from an accounting machine, or images consisting of user-selected fixed phrases. The hand stamp has a thermal print head and an ink ribbon for printing.
The direct printers known in the prior art are thus capable of printing an image onto an image receiving medium, and make use of a scanning print head. JP-6286227 discloses an electronic stamping apparatus which includes a pressure detection means that detects whether the pressure applied to an object is in a prescribed range, and a control means that controls scanning of a thermal transfer head based on the detection by the pressure detection means. This requires contact between the print head and the surface to be printed, in contrast to the printers described herein where the print head is spaced from the image receiving medium.
It is an aim of the present invention to improve the quality of images which are printed by the so-called direct printers. According to various aspects of the invention, this can be done in a number of different ways.
According to one aspect of the invention there is provided a printer comprising:
a housing arranged to be manually positioned on an image receiving medium at a printing location and defining an area over which printing is effected; a printing mechanism operable to effect printing over said area with the housing at said printing location; means for detecting relative movement between the image receiving medium and the housing during printing; and a controller for inhibiting printing when such relative movement is detected.
The means for detecting relative movement may be for example a scanner head, mouse ball etc. Thus, any relative motion detected during the print cycle may be used to interrupt or terminate the print cycle.
According to another aspect of the invention there is provided a printer comprising: a housing arranged to be manually position on an image receiving medium at a printing location and defining an area over which printing is effected; a printing mechanism operable to effect printing over said area with the housing at said printing location; means for detecting orientation of the housing with respect to the image receiving medium during printing; and a controller for inhibiting printing when an orientation other than a correct predetermined orientation is detected.
The means for detecting orientation of the housing can be for example a tilt sensor. Thus, the tilt sensor enables the print cycle to be inhibited unless the printer is positioned in the correct orientation.
According to a further aspect of the invention there is provided a printer comprising: a housing arranged to be manually positioned on an image receiving medium and defining an area over which printing is effected; a print head having a plurality of ink jet nozzles and mounted in said housing for travel within said housing relative to the image receiving medium to effect printing, said print head having an extent of travel which extends in a region outside the printing area; a controller for actuating said ink jet nozzles in said region as a maintenance procedure; and a set of absorbent strips arranged in said region for receiving ink ejected from the jet nozzles during the maintenance procedure.
By using the unprintable area for interim xe2x80x9cspittingxe2x80x9d, the print function can be maintained by preventing individual jets from blocking. The absorbent strips which are used to catch any drops of ink spat out may be replaceable.
According to a further aspect of the present invention there is provided a printer comprising: a housing arranged to be manually positioned on an image receiving medium at a printing location and defining an area over which printing is effected; a print head mounted in said housing for travel within said housing relative to the image receiving medium to effect printing; a motor for driving said print head under the control of a drive signal; and a controller for generating the drive signal for the motor wherein the controller includes fault condition detecting means which are operable to detect when the drive signal exceeds a predetermined limit and to inhibit printing in said fault condition.
In the described embodiment, the drive signal is an electric current which is supplied to the motor for causing movement of the print head. For an X-Y movement, there are two motors, one for moving the print head along an axis in an X direction and the other for moving the axis itself in a Y direction. Under normal printing loads, the drive current to the X-Y drive motors will follow a repeatable profile. Should the printing mechanism jam or encounter a higher resistance than normal, for example when printing on an uneven surface, the drive motor current will rise. By setting the boundaries that encompass the normal operating currents, current outside these boundaries may be detected as a fault condition and used to inhibit printing.
In another aspect, the invention provides a printing system comprising: a printing unit; a base station configured to receive the printing unit when not in use and having means for detecting return of the printing unit to the base station; and wherein a maintenance sequence for the printing unit is initiated on detection of return of the printing unit to the base station.
In another aspect the invention provides a printer comprising: a housing arranged to be manually positioned on an image receiving medium and having an opening defining an area over which printing is effected; a print head having a plurality of ink jet nozzles and mounted in said housing for travel within said housing relative to the image receiving medium to effect printing, said print head travelling at least within said opening and over said area to effect printing; and a cover removably attachable to said housing to close said opening when said printer is not in use.
For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made by way of example to the accompanying drawings.